Atomic-resolution STEM image denoising by total variation regularization
Atomic-resolution STEM image denoising by total variation regularization
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DOI：
10.1093/jmicro/dfac032
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发表时间：
2022-06-17
期刊：
影响因子：
1.8
通讯作者：
Ikuhara, Yuichi
中科院分区：
文献类型：
--
作者：
Kawahara, Kazuaki;Ishikawa, Ryo;Ikuhara, Yuichi
固态材料的原子分辨率电子显微镜成像是结构分析的强大方法。扫描透射电子显微镜（STEM）是直接观察材料中原子的常用技术之一。然而，有些材料很容易被电子束辐照损坏，当我们减少电子剂量以避免电子束损坏时，只能得到噪声图像。因此，低剂量 STEM 中的精确结构分析需要去噪处理。在本研究中，我们提出了全变分 (TV) 去噪算法来消除 STEM 图像中的量子噪声。我们定义了与图像对比度相对应的 STEM 图像的熵来确定超参数，我们发现存在一个使熵最大化的超参数。我们获得了沿 [001] 方向观察的 CaF2 的原子分辨率 STEM 图像，并执行了电视去噪。通过电视去噪，Ca 和 F 的原子柱清晰可见，并且 Ca 和 F 的原子位置确定的误差分别为 +/- 1 pm 和 +/- 4 pm。
Atomic-resolution electron microscopy imaging of solid-state material is a powerful method for structural analysis. Scanning transmission electron microscopy (STEM) is one of the actively used techniques to directly observe atoms in materials. However, some materials are easily damaged by the electron beam irradiation, and only noisy images are available when we decrease the electron dose to avoid beam damages. Therefore, a denoising process is necessary for precise structural analysis in low-dose STEM. In this study, we propose total variation (TV) denoising algorithm to remove quantum noise in an STEM image. We defined an entropy of STEM image that corresponds to the image contrast to determine a hyperparameter and we found that there is a hyperparameter that maximizes the entropy. We acquired atomic-resolution STEM image of CaF2 viewed along the [001] direction and executed TV denoising. The atomic columns of Ca and F are clearly visualized by the TV denoising, and atomic positions of Ca and F are determined with the error of +/- 1 pm and +/- 4 pm, respectively.